Spray dryer



Aug. 26, 1969 R WLLER ET AL SPRAY DRYER 2 Sheets-Sheet 1 Filed Jan. 17, 1968 INVENTOQS m M H M32, W W E D 1 M 8% mW J mm m J M M M ATTORNEYS Aug. 26, 1969 R. E. MILLER ETAL 3,463,400

SPRAY DRYER Filed Jan. 17, 1968 2 Sheets-Sheet 2 INVENTOIZS Roland E. Miller Clyde D. Wayne MM 1M, M, 72M

ATTOQNEY5 United States Patent 3,463,400 SPRAY DRYER Roland E. Miller, Orangeville, and Clyde D. Wayne, Wilmette, 11]., assignors to National Dairy Products Corporation, Chicago, 111., a corporation of Delaware Filed Jan. 17, 1968, Ser. No. 698,634 Int. Cl. Bb 3/10; B01d ]/22 US. Cl. 239-223 5 Claims ABSTRACT OF THE DISCLOSURE This invention relates generally to spray drying equipment and, more particularly, to vibration damping mounting assemblies utilized therewith.

Spray drying is a proven successful technique for large scale liquid removal operations. In a conventional practice of this method, a suspension or solution from which liquid is to be removed is atomized in a suitable device and propelled into a relatively large chamber through which heated air is also circulated. The small size of the droplets issuing from the atomizing device promotes extremely rapid evaporation and removal of liquid therefrom by the drying gas. There are thereby obtained dried particles which fall to the bottom of the chamber, from where they may be collected and removed.

One type of atomizer device which is particularly successful in certain spray drying operations is known generally as a centrifugal atomizer. A centrifugal atomizer normally incorporates a rotating member, commonly referred to as a disc, upon which the suspension or solution from which liquid is to be removed is permitted to impinge. Upon contacting the disc, the suspension or solution is hurled radially oil the disc at high speed by centrifugal force. The drying gas may be directed to intercept the sprayed droplets prior to or subsequent to their leaving the periphery of the disc.

Certain specialized spray drying operations may require a very high rotational speed for the rotary member or disc. By way of example and not limitation, in certain applications actual spray drying operations may be carried out with rotational speeds of the order of 16,000 r.p.m. Such speeds could conceivably be attained by utilizing a drive motor capable of providing an output speed the same as that of the atomizer drive shaft and mounting the motor in axial alignment with, and directly coupled to, the drive shaft. However, a motor capable of attaining such a high speed would be expensive, large, and therefore not completely satisfactory. Accordingly, it is conventional to utilize a motor of a lower speed and connect the atomizer shaft and motor through a belt and speed step-up pulley arrangement, with the motor mounted in parallel but offset relation to the atomizer drive shaft.

The rotating shaft of a centrifugal drier extends downwardly into the drying tank and is relatively long and of significant mass. Vibration problems are therefore, severe, not only those induced by slight imbalance of the shaft, but also those transmitted from external sources 3,463,400 Patented Aug. 26, 1969 such as other machinery and equipment located in the same building which induce vibrations in the shaft.

In order to isolate the atomizer from external vibration, the motor has been mounted on resilient pads and similar pads have been interposed between the shaft bearings and the top wall of the drier tank. However, when the drive belt connecting the pulleys of the atomizer shaft and motor shaft is tightened, the resilient pads yield, drawing the axes of the shafts out of parallel. Operation of the unit with the shafts thus disposed makes belt tracking difiicult, and causes difficulty in bringing the atomizer drive shaft to speed, and the angular disposition of the drive shaft shifts the spray pattern to such an extent that the dried product is not deposited uniformly at the bottom of the tank, thereby creating difficulties in removal.

It is an object of the present invention to provide an improved atomizing apparatus.

Another object of the invention is to provide an atomizing apparatus operable at high speed and wherein vibration problems are minimized.

It is another object of the invention to provide an atomizing apparatus wherein the driving motor and the atomizer drive shaft are offset and wherein wear on the bearings of the motor drive shaft and the atomizer drive shaft is minimized.

A further object of the invention is to provide an improved vibration damping means for use with atomizing apparatus.

Other objects of the invention will become apparent to those skilled in the art from the following description taken in connection with the accompanying drawings wherein:

FIGURE 1 is a side view, partially in section, illustrating a preferred form of apparatus constructed in accordance with the invention, showing the apparatus mounted for operation;

FIGURE 2 is a top view of the apparatus of FIGURE 1, with part broken away;

FIGURE 3 is an enlarged sectional elevational view of the area within the dotted circle A of FIGURE 1; and

FIGURE 4 is an enlarged sectional elevational view of the area Within the dotted circle B of FIGURE 1.

Very generally, the atomizing apparatus of the invention is utilized for mounting in an opening 11 in the top wall 12 of a drying tank 13. The apparatus comprises a rigid frame 14 which includes an annular plate 16 and an elongated outrigger 17 extending from the plate but elevated relative thereto. A centrifugal atomizer 18 is secured rigidly to and extends through the annular plate 16 and through the Wall opening 11 and includes a drive shaft 19 supported for rotation with respect to the frame assembly and provided with an atomizer disc 20 at its lower end. A motor 21 is mounted rigidly on the outrigger in horizontally spaced relation to the disc drive shaft 19 and includes a drive shaft 22 having an axis of rotation parallel with the axis of rotation of the drive shaft 19. The motor drive shaft 22 and the atomizer drive shaft 19 are drivingly coupled by a suitable belt. First vibration damping means 23, shown in detail in FIGURE 3, are distributed about the annular plate 16 intermediate the plate and the top wall 12 of the drying tank to isolate the plate from vibrations of the top wall. A second vibration damping means 24, seen most clearly in FIGURE 4, is positioned on the outrigger 17 outwardly of the motor 21 and secures the outrigger to the top wall of the drying tank while isolating the outrigger from vibrations of the top wall. Thus, although the mountings for the atomizer drive shaft and the motor (i.e., the annular plate 16 and the outrigger 17) are rigidly interconnected, they and the drive shaft 19 are insulated from vibrations of the drying tank 13.

Referring now particularly to FIGURES 1 and 2, the invention will be described in greater detail. The drying tank 13, of which a portion of the side wall 26 is shown in FIGURE 1, includes the top wall 12 formed of a plurality of cross beams 27 disposed intermediate lower plates 28 and upper plates 29. The opening 11 in the top wall 12 is defined by a length of angle iron stock rolled to form a ring 31 (FIG. 3) providing a cylindrical leg disposed perpendicular to the top wall 12 and an annular flange 32 integral therewith generally horizontally disposed and extending outwardly from the top edge of the leg. A metal hoop 33 extends upwardly from the outer periphery of the flange 32 and is welded to the edge of the upper plates 29 adjacent the opening 11 and also to the periphery of the flange 32.

An annular flat ring 34 of resilient damping material rests'on the ledge formed by the upper surface of the flange 32 and the annular plate 16 rests upon the upper surface of the ring and is secured thereto by the vibration damping means 23 (FIG. 3), explained in detail below. A pair of vertical and parallel plates 36 (FIG. I) extend upwardly from the annular plate 16 and are welded together and to the annular plate 16 to form a rigid construction.

As can be seen in both FIGURES 1 and 2, the outrigger 17 of the frame 14 is supported on and welded to the upper edges of the vertical plates and includes a pair of parallel beams 38 and 39 of L-shaped cross-sectional configuration. A pair of transverse channels 42 and 43 are welded between the beams adjacent the ends thereof opposite the plates 36 and a motor slide 44 rests flush against the top of the channels 42 and 43 and is secured thereto by bolts 46. The slide 44 slidably receives a motor mounting bracket 45 to which is secured the motor 21. A bolt 48 is provided for adjusting the position of the motor mount and, consequently, the motor, so that the belt connecting the motor shaft 22 and drive shaft 19 can be tightened.

The centrifugal atomizer 18 is supported by the frame 14 on the annular plate 16 thereof, and includes an outer elongated tubular housing 49 which is cylindrical in shape and which extends downwardly from an oval plate 51. The upper edge of the cylindrical housing 49 is welded to the plate 51 at the rim of a central opening therein. Four webs 52, two of which are shown in the drawings, extend radially from the cylindrical housing 49 and are welded to the plate to further secure the plate 51 to the housing.

The centrifugal atomizer 18 also includes the rotary drive shaft 19 which is journaled between an upper bearing 53 and a lower bearing, not shown. The upper bearing 53 is positioned near the upper end of the shaft 19 and is supported within the central opening of a plate 56 which is generally circular and is bolted to the plate 51 over the top of the housing 49. The lower bearing is supported near the lower end of the shaft 19, which rotates the hollow atomizer plate or disc 20 at high speed.

Thus, it can be seen that the atomizer 18 is rigidly secured to the annular plate 16, which is in turn rigidly secured to the beams 38 and 39 which rigidly support the motor 21. The atomizer drive shaft 19 and the motor drive shaft 22 are therefore maintained in parallel spaced relation to each other, a relationship which is preserved even when their connecting belt is tightened. Moreover, the atomizer drive shaft is maintained in accurate vertical disposition, as desired.

The liquid suspension or solution to be dried enters the centrifugal atomizer 18 through four feed lines 59 connected to a single inlet conduit, not illustrated, through a fitting 61 located at the top of the atomizer. Rigidity is maintained between the lines 59 by a brace plate 62. The lines pass into the interior of the housing 49 through suitable fittings in the bearing plate 56 and extend downwardly through the housing 49 to discharge their fluid contents into the interior of the rotating atomizer disc 20. Cool air is forced into the housing 49 near the upper end thereof through a conduit 66 by means of a blower 67 so as to prevent the bearings from reaching the high temperatures of the interior of the drying tank .13. The cooling air is discharged from the housing 49 in the vicinity of the disc 20.

The motor drive shaft 22 is coupled to the atomizer drive shaft 19 by a flexible drive belt 92 which extends between a motor drive pulley 93 on the motor drive shaft 22 and an atomizerdrive pulley 94 mounted on the atomized drive shaft 19. Means are provided for maintaining tension on the belt 92 and include (FIG. 2) an idler pulley 96 which engages the belt 92 and which is rotatably mounted adjacent one end of an L-shaped supporting arm 97. The opposite end of the arm 97 is attached to a shaft 99 pivotally supported in a housing 101.

In order to maintain the idler pulley 96 in contact with the belt 92, the arm 97 is provided with a cable 'attachment fitting 102. A cable 103 is attached to the fitting 102 and extends horizontally therefrom to the lower one of a pair of vertically aligned pulleys 104, only the top one of which is visible in FIGURE 2.. After passing around the lower one of the pulleys 104, the cable 103 is brought over the top one of the pulleys and then over the top of an outboard pulley 106, carried at the end of an arm 108. After passing over the pulley 106, the cable extends vertically downwardly and is attached to a weight support bar 111. A plurality of disc weights 112 are supported on the bar 111, the number and size of which can be varied to regulate the force applied to the belt 92 by the idler 96.

In order to isolate the centrifugal atomizer 18 from outside vibration, vibration damping mountings are utilized intermediate the annular plate 16 and the top wall 12 of the tank, and between the outrigger 17 and the top wall 12. More specifically, a damping mounting 23 is located at the peripheral of the annular plate 16 and includes (FIG. 3) the fiat resilient ring 34 extending around the periphery of the opening 11 and resting on the flange 32. The annular plate 16 rests on top of the ring 34, as previously pointed out. It may be noted that the outer diameter of the annular ring 16 is less than the inner diameter of the vertical metal hoop 33 so that the outer periphery of the annular plate 16 is spaced from the hoop 33 and not in contact therewith. The annular plate 16 is provided with openings at circumferentially spaced points, and similarly, the fiat ring is provided with an aligned opening at each of these points. A bolt 117 extends through each of the pairs of aligned openings and is threaded into the flange 32. Alternatively, the bolt may pass through the flange and a suitable nut may be provided on the underside of the flange. A buShing 118 of damping material surrounds the bolt 117 and is disposed in the opening in the annular plate 16. The bushing 118 is of a length that is slightly greater than the thickness of the annular plate 16. A flat ring 119 of damping material is positioned about the bolt 117 above the bushing 118 and annular plate 16. A flat washer 121 of metal or other rigid material surrounds the bolt 117 above the resilient ring 119 and a lock washer 122 is disposed between the head of the bolt 117 and the fiat rigid washer 121. A sleeve 123 of metal or other compressively rigid material extends along and encircles the bolt 117 within the bushing 118. The sleeve 123 extends effectively from the bolt head (although actually from the washer 121) to the flange 32.

The length of the sleeve 123 is selected such that the bolt 117 cannot be tightened sufliciently to significantly distend the damping material of the washer 119, bushing 118 and ring 113 out of shape so they could no longer perform a damping function. Thus, when the bolt 117 is tightened to bring the metal washer 121 down onto the upper edge of the sleeve 123, the damping material in the three aforementioned parts is compressed slightly, with the bushing 118 completely filling the space between the sleeve 123 and the annular ring 16. The annular ring is therefore securely mounted to the flange 32, but is completely isolated from vibration therein 'by the damping material. A preferred type of damping material is neoprene rubber due to its temperature resistance and oil resistance properties. Another satisfactory material is silicone rubber.

In order to completely isolate the frame 14, including the outrigger 17, from surrounding vibration, two vibration damping mountings 24, seen generally in FIGURE 1 and in detail in FIGURE 4, are utilized for securing the outrigger porton to the top 12 of the drying tank 13, one on each of the beams 38 and 39. The vibration damping mountings 24 are each positioned outwardly of the motor, that is, on the opposite side of the motor from the atomizer drive shaft 19.

Referring now to FIGURE 4, the details of one of the vibration damping mountings 24 may be seen. A metal mounting plate 124 rests upon the top of the beam 27 in an opening in the upper plate 29 of the top Wall 12. The upper plate 29 and the I-beam 27 are welded to the plate 124. A pad 126 of vibration damping material rests upon the metal mounting plate 124. A metal horizontally disposed mounting plate 127 rests upon the pad 126 and is secured to the underside of the beam 38 or 39 by a pair of vertical plates 128 and 129. The plates 128 and 129 are disposed at right angles to each other and are welded to each other, to the plate 127, and to the underside of the beam 38 or 39.

The plate 127 is provided with a pair of horizontally spaced openings therein. Similarly, the pad 126 is provided with a pair of openings aligned with the openings of the plate 127, respectively. A pair of bolts 136 and 137 extend through the respective pairs of aligned openings and both are secured in threaded openings in the metal mounting plate 124. A flat ring 138 of vibration damping material rests upon the plate 127 and surrounds each bolt 136 and 137. A bushing 139 surrounds each bolt within the opening in the plate 127. A flat rigid washer 143 and a lock washer 144 are positioned between the head of each bolt 136 :and 137 and the fiat resilient ring 138.

A sleeve 148 of compressively rigid material extends from the metal flat washer 143 to the top surface of the metal pad 124 in surrounding relation to each bolt. As was the case in connection with the vibration damping mounting 23 in FIGURE 3, when the bolts 136 and 137 are tightened, the preselected length of the sleeves 148 and 149 provides for the desired amount of compression on the vibration damping material in the pad 126, the bushing 139 and the flat rings 138. The result is effective isolation of the rigid weldment of plates from the metal pad 124. As was the case with the previously described vibration damping mounting 23, the vibration damping material is preferably neoprene rubber or silicone rubber.

One factor in the avoidance of self-induced vibrations is believed to be the rigidity which the apparatus provides between the motor drive shaft and the atomizer drive shaft. Forces transmitted through the belt drive which tend to pull the ends of the respective drive shafts toward each other with resultant shaft misalignment are resisted by the extremely rigid mounting of both drive shafts on a unitary frame structure. Aiding rigidity is the mounting of the pulley 94 adjacent the bearing 53, because the latter is rigid with respect to the motor and shaft flexure due to belt forces at that point is minimized.

It may therefore be seen that the invention provides an improved atomizing apparatus and improved vibration damping means for use therewith. The apparatus is operable at high speed and minimizes vibration problems.

Various modifications of the invention, in addition to those shown and described herein, will become apparent Various of the features of the invention believed to be novel are set forth in the following claims.

What is claimed is:

1. Atomizing apparatus for mounting in an opening in the top wall of a drying tank, comprising a rigid frame including a plate and an elongated outrigger rigidly secured to and extending from said plate, means securing said plate to the top wall of the drying tank over the opening therein, said plate securing means being capable of minimizing the transmission of vibrations between said plate and the top wall of the tank, means securing said outrigger to the top wall of the drying tank in spaced relation to said plate, said outrigger securing means being capable of minimizing the transmission of vibrations between said outrigger and the top wall of the tank, a centrifugal atomizer rigidly secured to said plate including an atomizer drive shaft supported for rotation with respect to said plate and extending through the opening in the top wall of the tank, a motor mounted rigidly on said outrigger in spaced relation to said atomizer drive shaft and having a motor drive shaft with a rotational axis disposed in parallel relation to the rotational axis of said atomizer drive shaft, and means coupling said motor drive shaft to said atomizer drive shaft for driving same whereby the axis of said atomizer drive shaft and of said motor drive shaft are maintained in fixed relative position by said rigid frame and together therewith form an integral unit insulated from the drying tank so as to minimize the transmission of vibrations therebetween.

2. Atomizing apparatus according to claim 1, wherein said plate securing means and said outrigger securing means each include a compressible damping material interposed between said frame and the top wall of the tank, a bolt passing through said frame and the top wall and secured by threads to the topwall, said bolt including a shoulder engageable with said. damping means and capable of placing the dampening means in compression when said bolt is tightened, and means for limiting the extent to which said bolt can be tightened so as to limit the degree of deformation of said damping material.

3. Atomizing apparatus according to claim 2, wherein a bushing of damping material surrounds that portion of said bolt located within said frame, and wherein a sleeve of compressibly rigid material is positioned coaxially about said bolt and within said bushing and ex- .tends efiectively from the head of said bolt to the upper surface of the top wall, said sleeve being of such a length as to limit the degree to which said bolt can be tightened to that which will produce a predetermined amount of deformation of said damping material.

4. Atomizing apparatus according to claim 3 wherein said means securing said plate to the top wall of the tank includes a plurality of bolts distributed about said plate, wherein said layer of damping material between said plate and the top wall comprising a flat ring, and wherein a Washer formed of a damping material is located between said plate and the head of each of said bolts.

5. Atomizing apparatus according to claim 2 wherein said damping material comprises neoprene rubber.

References Cited UNITED STATES PATENTS 2,473,035 6/1949 Meade et al. 239-224 EVERETT W. KIRBY, Primary Examiner US. Cl. X.R. 159-6 

